Plastic utility trucks are used in many applications, of which hotel or hospital laundry trucks serve as one example. A hotel laundry truck must hold a large quantity of heavy, wet laundry, such as towels. Wet hotel linens gathered in a laundry truck can accumulate and be very heavy, imparting substantial loads on the plastic truck. Plastic laundry trucks will tend to sag under such heavy weights. To overcome the tendency of plastic trucks to sag under such weights, base chassis structures are bolted or glued to the bottom of the truck to increase the strength of the truck. FIG. 1 shows such an arrangement. The utility truck 1 is rectangular in shape, being longer in the front-back direction than side-to-side. The truck 1 is made from molded plastic, as practiced and understood in the art. To increase the load bearing capacity of the truck, a supplemental chassis base 3 is secured to the bottom 2 of the truck. The chassis base 3 is usually made of metal or plastic and is bolted or glued to the truck's bottom 2. At each of the four corners of the chassis base 3, caster wheels 4 are bolted to the base.
A utility truck with such a supplemental chassis base structure requires the construction of the separate chassis. Steel bases are commonly used for this purpose. To maximize strength provided by the metal chassis base to the plastic truck, the metal chassis must have a large surface area, thereby requiring a substantial quantity of metal. Most such metal chassis base structures are constructed of steel, which is expensive. In most applications, the metal chassis base will be prone to oxidation, and this is especially true of a steel chassis in a laundry truck, since the laundry will be wet and promote rust. To prevent the metal from oxidizing, the chassis base is usually powder coated to seal the metal from the surrounding environment. However, chips in the coating are likely to occur during use and allow rust incursion. The construction and powder coating of a metal chassis base is expensive. As noted above, plastic supplemental chassis bases are sometimes used, but these will not provide as much strength as a steel chassis and, nevertheless, still require the manufacture of a separate chassis structure.
In addition to the cost of the separate chassis base structure, the assembly of the molded plastic truck and the separate chassis base requires several additional manufacturing steps after the plastic truck has been removed from the mold. These assembly steps are labor intensive. Also, the chassis base is often attached to the plastic truck with bolts that extend through the bottom of the truck, which creates passages through which liquid can escape. To prevent this, sealant must be applied around these through-bolt mountings, thereby increasing the cost of manufacturing the truck and creating a potential area through which leaks may develop over time as the sealant degrades.
What is needed is a utility truck with a chassis incorporated into the plastic truck, thereby eliminating the need for a separate chassis base structure. Also needed is a method of manufacturing such a truck with a chassis incorporated into the plastic truck during molding. Also needed is such a unitary plastic truck and molded-in reinforcing chassis structure that uses less reinforcing material, provides a lighter truck, yet provides superior structural strength and load-carrying capacity.